1. Field of the Invention
The present invention relates to a radiation thermometer.
2. Description of the Prior Art
For the purpose of measuring a body temperature in a short period of time, a radiation thermometer which selects an eardrum as a measurement site and measures a temperature of the eardrum in a non-contact manner has been already proposed.
An example is a radiation thermometer which is disclosed in Japanese Laid-open Patent Publication No. 28524/1990. This radiation thermometer allows a front end of a probe portion, which comprises a window member at a front end and an infrared ray sensor at a rear end, to be inserted into an external acoustic opening, so that an infrared ray from the eardrum is received by the infrared ray sensor through the window member, and the temperature of the eardrum, i.e. the body temperature, is measured based on the intensity of the received infrared ray.
Since this type of radiation thermometer measures a body temperature based on the intensity of an infrared ray from the eardrum, the cleanliness of the optical system which receives the infrared ray has influence on measurement accuracy. However, an external acoustic opening becomes dirty because of earwax and the like, and therefore, measuring a body temperature several times causes a problem in that the window member serving as an optical system of the front end of the probe portion is gradually smudged. Further, it is unhygienic where more than one person shares the same radiation thermometer.
To solve this problem, the radiation thermometer disclosed in Japanese Laid-open Patent Publication No. 28524/1990 comprises a probe cover designed to cover the front end of the probe portion which is inserted into an external acoustic opening. The probe cover prevents the probe portion of the radiation thermometer from directly contacting the external acoustic opening. In addition, since the probe cover is disposable after each measurement of a body temperature, there is no problem in that a dirty optical system deteriorates a measurement accuracy, and there is no hygienic problem.
However, when -a probe cover is used as in the case of the radiation thermometer disclosed in Japanese Laid-open Patent Publication No. 28524/1990 described above, a new probe cover is necessary each time a body temperature is measured, which is costly. Hospitals, in particular, which need to measure body temperatures frequently, must bear a considerable running cost.
Further, since a conventional radiation thermometer which uses probe covers requires discarding the probe cover each time a body temperature is measured, it is necessary to procure new probe covers often, which is labor-consuming.
To solve this problem, the present applicant has proposed a radiation thermometer having a probe portion of a waterproof structure in Japanese Patent Application No. 244970/1992.
In the radiation thermometer disclosed in Japanese Patent Application No. 244970/1992, as the probe portion has a waterproof structure, it is possible to disinfect and clean a portion of the front end of the radiation thermometer to be put into the external acoustic opening by using alcohol or a detergent after measurement of a body temperature has been finished. Therefore, it is possible to maintain the radiation thermometer always in a hygienic condition. Further, it is possible to avoid deterioration in the accuracy of measuring a temperature due to the dirtiness of the optical system. Further, as a probe cover is not necessary, it is possible to cut the running cost involved in the purchase of the probe covers.
In the above-described radiation thermometer, a body temperature is measured by receiving an infrared ray from the eardrum or the external acoustic opening by an infrared ray sensor and by detecting the intensity of the infrared ray.
As described above, the conventional radiation thermometer measures the body temperature assuming that an infrared ray incident to the infrared ray sensor is only from the eardrum or the external acoustic opening.
However, the inventor of the present application has found that a temperature is measured at a lower level than an actual temperature, when a temperature was measured by using the conventional radiation thermometer. Therefore, in an extreme case, there has been such risk that the conventional radiation thermometer displays a measured body temperature at a lower level even when a person has a fever due to a cold or the like and a decision is made that he has a normal body temperature.
In the light of the above discussion, it is an object of the present invention to provide a radiation thermometer that is designed to measure a body temperature more accurately than a conventional radiation thermometer.
In order to achieve the above object, the present invention is characterized in that a radiation thermometer comprises: infrared-ray detecting means; a probe portion having a front end to be inserted into a hole portion of a living being and an introduction opening provided at the front end for guiding an infrared ray emitted from the hole portion of the living being to the infrared-ray detecting means; temperature-measuring means for measuring a temperature of the probe portion; and calculating means for calculating a body temperature of the living being based on detected values from the infrared-ray detecting means and the temperature-measuring means, wherein the calculating means has body temperature calculating means for calculating a body temperature of the living being according to a predetermined arithmetic expression based on an emissivity of the hole portion of the living being when the emissivity is less than 1, an output of the infrared-ray detecting means and an output of the temperature-measuring means.
Further, the invention is characterized in that the probe portion has a shape to fill almost the whole hole portion of the living being when the probe portion is inserted into the hole portion of the living being.
Further, the invention is characterized in that the body temperature calculating means includes a process for dividing an output of the infrared-ray detecting means by the emissivity.
Further, the invention is characterized in that the temperature-measuring means serves as temperature-measuring means for measuring a temperature of the infrared-ray detecting means.
Further, the invention is characterized in that the temperature-measuring means comprises a first temperature-measuring means for measuring a temperature of the probe portion and a second temperature-measuring means for measuring a temperature of the infrared-ray detecting means.
Further, the invention is characterized in that the predetermined arithmetic expression is
Tb=(T04+Vb/Ke)xc2xc
where Tb represents a temperature of the hole portion of the living being, T0 represents a temperature of the infrared-ray detecting means, Vb represents an output of the infrared-ray detecting means, K represents a constant, and e represents an emissivity of the hole portion of the living being.
Further, the invention is characterized in that the predetermined arithmetic expression is a primary expression that approximates a temperature (Tb) of the hole portion of the living being by a temperature (T0) of the infrared-ray detecting means, an output (Vb) of the infrared-ray detecting means, and an emissivity (e) of the hole portion of the living being.
Further, the invention is characterized in that the predetermined arithmetic expression is
Tb=T0+Vb/K1e
where Tb represents a temperature of the hole portion of the living being, T0 represents temperature of the infrared-ray detecting means, Vb represents an output of the infrared-ray detecting means, K1 represents a constant, and e represents an emissivity of the hole portion of the living being.
Further, the invention is characterized in that the predetermined arithmetic expression is
Tb={[Vb/K+T04xe2x88x92(1xe2x88x92e)Tp4]/e}xc2xc
where Tb represents a temperature of the hole portion of the living being, Vb represents an output of the infrared-ray detecting means, K represents a constant, T0 represents a temperature of the infrared-ray detecting means, e represents an emissivity of the hole portion of the living being, and Tp represents a temperature of the probe portion.
Further, the invention is characterized in that the probe portion has a light-guiding pipe for guiding an infrared ray emitted from the introduction opening to the infrared ray sensor and case means for covering the light-guiding pipe, with a space formed between the light-guiding pipe and the case means, and the second temperature-measuring means is provided between the case means and the light-guiding pipe such that the second temperature-measuring means is in contact with the case means but is not in contact with the light-guiding pipe.
Further, the invention is characterized in that a member of the front end of the probe portion has a thermal capacity to such extent that a temperature does not change suddenly during a period of time required for calculating a body temperature of the living being.
Further, the invention is characterized in that the front end of the probe portion has a window member provided at the introduction opening.
Further, the invention is characterized in that the window member is made of calcium fluoride, silicon or barium fluoride having a thickness of 0.3 mm or more.
Further, the invention is characterized in that the hole portion of the living being is an external acoustic opening of a human being, and the emissivity is set to 0.90 to 0.98.
Further, the invention is characterized in that the radiation thermometer has emissivity setting means for setting the emissivity.
Further, the invention is characterized in that the radiation thermometer has peak value detecting means for detecting a peak value of the infrared-ray detecting means, and an output of the infrared-ray detecting means that is used by the calculating means for the calculation is the peak value.
Further, the invention is characterized in that a radiation thermometer comprises: infrared-ray detecting means; a probe portion having a front end to be inserted into a hole portion of a living being and an introduction opening provided at the front end for guiding an infrared ray emitted from the hole portion of the living being to the infrared-ray detecting means; temperature-measuring means for measuring a temperature of the probe portion; emissivity selecting means for selecting either an emissivity of the hole portion of the living being when the emissivity is less than 1 or 1.00 as the emissivity of a temperature-measured object; and calculating means for calculating a temperature of the temperature-measured object based on an output of the infrared-ray detecting means, an output of the temperature-measuring means, and an emissivity selected by the emissivity setting means.
Further, the invention is characterized in that the radiation thermometer has a measuring switch for starting a measuring operation, and the emissivity selecting means selects an emissivity according to the operation of the measuring switch.